Thanks, I went to the Sundstrom Safety site and looked at the pdf's of the various chemical cartridges and the diagrams all looked the same -- mostly activated carbon. Chemical cartridge SR 232, OV/SD/CL/HC/HF cartridge leaflet pdf is one. They all look similar, but who knows what else is in there.

Fortunately, all I ever use is the particle filter and all ever had to replace is a couple pre-filters which are cheap. As for all the chemicals listed, avoidance is my first choice and for me living where I live that's not a problem. No tracks within many miles -- then again, an interstate is just up the street...